What's the Difference Between a Newt and Salamander?

The eastern red-spotted newt is a member of Salamandridae, the family that comprises all true salamanders and newts. julie persons photography/Getty Images

If you've ever gone hiking or backpacking east of the Mississippi River, you might've seen a little amphibian called Notophthalmus viridescens, or the eastern newt.

"Little" is the operative word here. About 3 to 5 inches (7.6 to 12.7 centimeters) long, the eastern newt could curl up on the palm of your hand.

Eastern newts start out as larvae. At birth, they hatch from their eggs in calm, fresh water. This is also where they'll spend most of their time as adults. But a strange thing happens during adolescence.

Between the ages of 3 and 4 weeks old, many of these newt larvae turn into "red efts." It's a temporary phase — marked by physical changes that influence behavior. Teenage humans, you know what we're talking about.

Red efts have rough, bright orange skin and webless fingers. Abandoning the cool ponds of their childhoods, they become landlubbers who hang out on forest floors or mossy meadows. With maturity, the skin moistens. The orange fades into a dull shade of green. And the tail gets more paddle-shaped, making it a perfect swimming tool. What was once a crawling eft has transitioned into an aquatic adult, a full-grown newt ready for reproduction.

Before they return to the water, young eastern newts are easily mistaken for a larger, unrelated species: the red salamander (Pseudotriton ruber). Found in many of the same states, it's yet another amphibian with spots, four legs and a long tail.

Oh and, déjà vu, it comes in an orange-red color. (Sometimes.)

So why do we call one animal a "newt" and the other a "salamander?" And what separates the former from the latter?

Eastern newts start out as larvae and at the ages of 3 and 4 weeks old, many of these newt larvae turn into "red efts."
Cyndi Monaghan/Getty Images

Life in Two Worlds

"The simple answer is that all newts are salamanders but not all salamanders are newts," says herpetologist and author Whit Gibbons in an email.

Salamanders are classified as amphibians. Like all other amphibians (i.e., frogs), they have backbones and three-chambered hearts.

Other traits are skin-deep. Amphibians tend to lack scales, for instance. They're also capable of breathing through several different means. Some species have lungs, some use feathery gills and many absorb oxygen straight through the skin. Employing all three methods at once isn't unheard of.

The word "amphibian" comes from a Greek term that means "double life." Apart from the fully aquatic species, most amphibians divide their lives between land and water. Hence the name.

Field guides tend to call amphibians "cold-blooded." Unlike mammals, they can't produce body heat internally or maintain a constant body temperature. Instead, they have to derive warmth from their environment.

But "cold-blooded" is really just an informal descriptor. It's not a label biologists use when they talk among themselves; if you want to get technical, amphibians are more accurately called "ectothermic poikilotherms."

The word "newt" is kind of informal, too. At least scientifically.

All in the "Subfamily"

David Wake is a professor of integrative biology at the University of California, Berkeley and the director of the AmphibiaWeb Project, a virtual amphibian database.

"Newt is a narrow term that originates from the Middle English newte, which is a doublet of efte," Wake says in a separate email exchange. "It is a term," he adds, "that has no scientific meaning and is a holdover from the Middle Ages."

Salamanders are divided up into 10 families. One of these is known as the Salamandridae. Widespread in Europe, the Salamandrids also reside in parts of East Asia and far-north Africa. Over in the Western Hemisphere, some species live along North America's Pacific Coastline. Others are pretty common on the opposite side of the continent.

The Salamdridae family is big enough to have subfamilies of its own. Far and away, the largest is the so-named Pleurodelinae, a group that includes 109 different species.

By popular tradition, the label "newt" has been reserved for various salamanders in the Pleurodelinae subfamily.

So returning to the question we posed earlier, our friend the eastern newt is a member of the Pleurodelinae. The red salamander is not.

Gibbons says a lot of Eurasian newts "such as fire-bellied newts, emperor newts, warty newts, marbled newts and red-tailed knobby newts" have become popular in the pet trade.

Your neighborhood pet store is less likely to carry North American newt species. According to Gibbons, those New World animals "are referred to as 'newts' rather than 'salamanders' because of general familiarity [with] the name by the populace within their geographic region."

Unlike newts and a lot of other salamanders, the red salamander doesn't have lungs.
Zoonar RF/Getty Images/Zoonar RF

Lungs and Toxins

Despite their unofficial status as a group, newts do tend to share a few key traits.

Remember the red salamander (i.e., Pseudotriton ruber)? Well like a lot of other salamanders, it doesn't possess lungs. But newts develop lungs as they grow up. Furthermore, many newts have rougher skin than your typical salamander.

That's not a hard-and-fast rule: Wake says salamanders in the genus Pachytriton are called newts despite being "fully aquatic and smooth skinned."

"No accounting for taste," observes Wake.

Speaking of taste, Gibbon tells us newts often harbor "poison glands in the skin that make them mildly or highly toxic to other animals, including humans." Look no further than the Pacific newts of western North America (genus: Taricha).

"Amphibian skin is loaded with different kinds of toxins, the most potent being tetrodotoxin, the toxin in puffer fish," Wake says.

How potent are we talking? Tetrodotoxin (TTX for short) is more toxic to people than cyanide. More than 1,000 times more toxic, in fact.

A Cold War, Writ Small

Pacific newts use tetrodotoxin to ward off predators. A single rough-skinned newt (Taricha granulosa) carries enough TTX to kill upward of 2,000 kingfishers, 200 herons — or 100 people!

Yet the chemical weapon isn't always effective. Common garter snakes who live in this newt's natural range can swallow the toxic animals and live to tell the tale. Their TTX resistance set off a game of evolutionary one-upmanship.

Rough-skinned newts are small and slow, capable of neither fight nor flight. Chemical defenses are critical to their survival as a species. So the presence of TTX-tolerant garters was a real game-changer. Natural selection pushed the newts to repel these snakes by increasing their toxicity levels.

In response, later generations of garters became even more resistant to TTX. Anyone born during the Cold War should know where this is going. Before too long, absurdly toxic newts were facing down garter snakes who could stomach unbelievably high amounts of TTX.

Greater toxicity prompted greater tolerance — and vice versa. On and on the cycle went, spiraling into a biological arms race between the two species that still rages today. Escalation's a heck of a thing.